Improvement in step-ladders



. the attaching-bracket.

@UNITED STATES in ya .Marvin N. LovELn, or ERIE, PENNSYLVANIA, AssIeNoR oF'oNE-HALF HIS RIGHT TO FRANK F. ADAMS, OF SAME PLACE.

:fr IMPROVEMENT IN STEP- I ADDERS.

Specification forming part of Letters Patent No. 136,659, dated Marl-h 11, 1873.

To all whom it may concern:

Be it known that I, MELvm N. LOVLL, of

, Erie, in the county of Erie and State of Penn- Vder to the body of the same, in such a mannerthat when the legs or props are extended for use they shall be so locked within the-hinging device that they can neither be extended further nor closed up without lifting the ladder up sufficiently to allow the said legs or props to be raised from the ground; and, also, in so constructing the said hinging device that 'it shall form a part of the bracket at the top of the ladder.

In the accompanying illustration I4 have shown two modes of constructing my device, one of which I believe to be the equivalent of the other. I have devised other forms of construction, all of which are equivalents, and all of which, as `do the two forms shown, embody the essential features of my device as set forth above, to wit, that when the props or legs are extended for use, they shall be so locked within the hinging device that they can neither be extended further nor closed up without lifting the ladder up sufficiently to allow the said legs or props to be raised from 4the ground, or at least to about that extent. f

The accompanying illustration represents my hin ging device constructed in two forms. Thus, Figure lshows what I call the socket or angeform, and Fig. 2 shows what I call the slot form.

In Fig. 1, A is the face of the bracket at the top of the ladder, and is known, Ibelieve, as B is the leg or prop. C G G C and C C C' are anges, or, rather, are one continuous ange, which is so arranged or directed as to form a double or compoundsocket for the endof the propB. Thus, C C C C form one socket, and C C C form the other socket. These sockets are at an angle to each other, andA both are at an angle to the plane of the top step of the ladder. One, that formed by the flanges (1 C G C, is placed at the same angle to the plane of the top step' that the prop maintains when in supporting position 5 hence I call this the workin g socket. The other, that formed by the flanges C C C', is placed at the same angle to the plane of the top step that the prop maintains when it is folded and out of use; hence I call this the idle socket. Neither of these sockets are perfect in themselves, although the workin g socket performs all the duties of a perfect socket. They are severally imperfect in that they are jointly a compound socket. The iiange is bridged and strengthened by the strap D. The leg or prop B is attached to this device as follows: The end is first placed in the idle socket, as shown by the dotted lines, and the screw b is inserted in the leg B above the strap D, as shown by the dotted lines. `This screw acts as a pivot-pin for the leg, and also as a stoppin to prevent the leg from dropping out of the socket. The leg thus arranged is free to swing; but when thrown out to its extended position and allowed to rest on the ground the upper end enters the working socket, and the leg then takes the position shown in Fig. 1 by the full lines. Once in this position it is entirely locked as long as the ladder is in working position-Le., the leg can neither be extended further nor closed up without lifting the ladder sumciently to allow the legs or props to be raised from the ground, or at least to about that extent. In other Words the position of the center of motion of the prop must be changed.

It will be observed that before the ladder can be'used the prop is prepared to enter the working socket; and that when in that it' is locked; and that that result is obtained automatically; and that the unlocking, when accomplished, is also automatic; and that to accomplish these results the hingiu g device must be so constructed that the leg or prop shall change the position of the center of motion whenever it changes from an active to an idle position.

Having thus fully described the nature and obj ects as well as the mechanical operation of my device, and also one form of constructing the same, I come now to the equivalent form shown in Fig. 2, Where Ais the attachingbracket, and B the prop. The dotted lines show the positions assumed by the prop. The

pivot-pin b is placed in. aislot, C, ,the direction of .which is parallel to that of the prop` part of the attaching-bracket A, and the props are always locked within the hinging device.

What I claim as new is as follows:

1. A device for hinging thel props orlegsof v step-ladders, whereby the said props are automatically locked when extended by changing the position of the center of motion of the said props, substantially as shown and described. 2. A device for hinging the props of stepladders and automatically locking the same,

,substantially as herein shown, the same forming a part ot' the attaching-bracket7 as set forth.

MELVIN N. LOVELL.

Witnesses:

JNO. K. HALLooK, JOHN A. SMITH. 

